linux-user: fix fork()

[Qemu-devel] [PATCH] linux-user: fix fork()

Posted by Laurent Vivier 7 years, 2 months ago

Since commit 5ea2fc8 ("linux-user: Sanity check clone flags"),
trying to run fork() fails with old distro on some architectures.

This is the case with HP-PA and Debian 5 (Lenny).

It fails on:

         if ((flags & CSIGNAL) != TARGET_SIGCHLD) {
             return -TARGET_EINVAL;
         }

because flags is 17, whereas on HP-PA, SIGCHLD is 18.
17 is the SIGCHLD value of my host (x86_64).

It appears that for TARGET_NR_fork and TARGET_NR_vfork, QEMU calls
do_fork() with SIGCHLD instead of TARGET_SIGCHLD.

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
---
 linux-user/syscall.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index f569f82..4d85355 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7680,7 +7680,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         break;
 #ifdef TARGET_NR_fork
     case TARGET_NR_fork:
-        ret = get_errno(do_fork(cpu_env, SIGCHLD, 0, 0, 0, 0));
+        ret = get_errno(do_fork(cpu_env, TARGET_SIGCHLD, 0, 0, 0, 0));
         break;
 #endif
 #ifdef TARGET_NR_waitpid
@@ -10490,7 +10490,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
 #endif
 #ifdef TARGET_NR_vfork
     case TARGET_NR_vfork:
-        ret = get_errno(do_fork(cpu_env, CLONE_VFORK | CLONE_VM | SIGCHLD,
+        ret = get_errno(do_fork(cpu_env,
+                        CLONE_VFORK | CLONE_VM | TARGET_SIGCHLD,
                         0, 0, 0, 0));
         break;
 #endif
-- 
2.9.3

Re: [Qemu-devel] [PATCH] linux-user: fix fork()

Posted by Peter Maydell 7 years, 2 months ago

On 16 February 2017 at 17:37, Laurent Vivier <laurent@vivier.eu> wrote:
> Since commit 5ea2fc8 ("linux-user: Sanity check clone flags"),
> trying to run fork() fails with old distro on some architectures.
>
> This is the case with HP-PA and Debian 5 (Lenny).
>
> It fails on:
>
>          if ((flags & CSIGNAL) != TARGET_SIGCHLD) {
>              return -TARGET_EINVAL;
>          }
>
> because flags is 17, whereas on HP-PA, SIGCHLD is 18.
> 17 is the SIGCHLD value of my host (x86_64).
>
> It appears that for TARGET_NR_fork and TARGET_NR_vfork, QEMU calls
> do_fork() with SIGCHLD instead of TARGET_SIGCHLD.
>
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
> ---
>  linux-user/syscall.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index f569f82..4d85355 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -7680,7 +7680,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>          break;
>  #ifdef TARGET_NR_fork
>      case TARGET_NR_fork:
> -        ret = get_errno(do_fork(cpu_env, SIGCHLD, 0, 0, 0, 0));
> +        ret = get_errno(do_fork(cpu_env, TARGET_SIGCHLD, 0, 0, 0, 0));
>          break;
>  #endif
>  #ifdef TARGET_NR_waitpid
> @@ -10490,7 +10490,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>  #endif
>  #ifdef TARGET_NR_vfork
>      case TARGET_NR_vfork:
> -        ret = get_errno(do_fork(cpu_env, CLONE_VFORK | CLONE_VM | SIGCHLD,
> +        ret = get_errno(do_fork(cpu_env,
> +                        CLONE_VFORK | CLONE_VM | TARGET_SIGCHLD,
>                          0, 0, 0, 0));
>          break;
>  #endif

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Re: [Qemu-devel] [PATCH] linux-user: fix fork()

Posted by Philippe Mathieu-Daudé 7 years, 1 month ago

On 02/16/2017 02:37 PM, Laurent Vivier wrote:
> Since commit 5ea2fc8 ("linux-user: Sanity check clone flags"),
> trying to run fork() fails with old distro on some architectures.
>
> This is the case with HP-PA and Debian 5 (Lenny).
>
> It fails on:
>
>          if ((flags & CSIGNAL) != TARGET_SIGCHLD) {
>              return -TARGET_EINVAL;
>          }
>
> because flags is 17, whereas on HP-PA, SIGCHLD is 18.
> 17 is the SIGCHLD value of my host (x86_64).
>
> It appears that for TARGET_NR_fork and TARGET_NR_vfork, QEMU calls
> do_fork() with SIGCHLD instead of TARGET_SIGCHLD.
>
> Signed-off-by: Laurent Vivier <laurent@vivier.eu>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>  linux-user/syscall.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index f569f82..4d85355 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -7680,7 +7680,7 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>          break;
>  #ifdef TARGET_NR_fork
>      case TARGET_NR_fork:
> -        ret = get_errno(do_fork(cpu_env, SIGCHLD, 0, 0, 0, 0));
> +        ret = get_errno(do_fork(cpu_env, TARGET_SIGCHLD, 0, 0, 0, 0));
>          break;
>  #endif
>  #ifdef TARGET_NR_waitpid
> @@ -10490,7 +10490,8 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>  #endif
>  #ifdef TARGET_NR_vfork
>      case TARGET_NR_vfork:
> -        ret = get_errno(do_fork(cpu_env, CLONE_VFORK | CLONE_VM | SIGCHLD,
> +        ret = get_errno(do_fork(cpu_env,
> +                        CLONE_VFORK | CLONE_VM | TARGET_SIGCHLD,
>                          0, 0, 0, 0));
>          break;
>  #endif
>